Hello Jan,
----- Original Message -----
> From: Jan Kaluza <jkaluza@xxxxxxxxxx>
> Subject: Re: logrotate(8) and copytruncate as default
>
> Right now, without locking, logrotate would loss more messages if the
> logs are big, because copying takes more time. It would be interesting
> to mention the file size in your tests too.
===
#!/bin/sh
#
# flockexp.sh: is a simple experiment to create a large log file and
# copy-truncate it when its size reaches a predefined limit.
#
if [ $# -lt 2 ]; then
echo "Usage: $0 <output-file> <maxsize>";
exit 0;
fi
# main
{
> $1;
logsize=$2;
watch "if [ \`stat -c '%s' $1\` -gt $logsize ]; " \
"then flock -x $1 -c 'cp $1 $1.1; > $1'; fi" > /dev/null &
count=0;
while (true);
do
count=`expr $count + 1`;
echo `date "+%d %a %Y %T"` $count `grep 'MemFree' /proc/meminfo`;
done >> $1;
}
===
I tried it with different file sizes. It starts showing data loss as size grows > 2MB.
===
$ stat -c '%s' test.log test.log.1
418065
2007074
$
$ tail -n 4 test.log.1
28 Fri 2013 17:20:28 42937 MemFree: 3655640 kB
28 Fri 2013 17:20:28 42938 MemFree: 3655580 kB
28 Fri 2013 17:20:28 42939 MemFree: 3655068 kB
28 Fri 2013 17:20:28 42940 MemFree: 3655436 kB
$
$ head -n 4 test.log
28 Fri 2013 17:20:28 42942 MemFree: 3655428 kB
28 Fri 2013 17:20:28 42943 MemFree: 3655448 kB
28 Fri 2013 17:20:28 42944 MemFree: 3655812 kB
28 Fri 2013 17:20:28 42945 MemFree: 3655824 kB
===
I guess kernel buffers start dropping writes after very short limit.
---
Regards
-Prasad
http://feedmug.com
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